Hi Everyone, I am stuck with a simple problem. Suppose I have a vector x, and I want to calculate y[i]=x[i+1]-x[i], it is very easy. I just need to write y<-x[2:length(x)]-x[1:length(x)-1]. Now if I know y, and want to know the vector x defined by x[i]=x[i-1]+y[i-1] for all i, how can I do this without a loop? Thanks, Geoffrey _______________________________________________________ The information in this email or in any file attached hereto is intended only for the personal and confidential use of the individual or entity to which it is addressed and may contain information that is proprietary and confidential. If you are not the intended recipient of this message you are hereby notified that any review, dissemination, distribution or copying of this message is strictly prohibited. This communication is for information purposes only and should not be regarded as an offer to sell or as a solicitation of an offer to buy any financial product. Email transmission cannot be guaranteed to be secure or error-free.